Only one time (to my knowledge). I was at a trade show at the convention center in Birmingham (AL) and was in an out of the way bathroom with no dividers. A guy had peed a few urinals down from me and I saw his cock. When he left I started jerking off and about half way to climax, another guy came in and stood two down from me. I was still semi-erect but had stopped beating when the door opened. I just stood there as if I was pissing and noticed he was looking over at my cock and started playing with himself, so I started again. When I shot my load, he was still playing with himself. I went to the sink to wash my hands and I could see in the mirror his body stiffning so I assume he shot his load too. I left before he did but did see him later at his booth. He was a vendor.